1. Technical Field
The invention relates to liquid automatic dishwashing detergents. More particularly, this invention relates to liquid automatic dishwashing detergents with superior environmental and human safety as well as superior cleaning efficacy and stability.
2. Background Information
Powdered automatic dishwashing detergents are well suited to the task of effectively cleaning dishes in a home dishwashing machine. Such products typically contain relatively large amounts of phosphate builders, chlorine bleaches, and alkali. In addition, liquid automatic dishwashing detergents (LADDs) have been developed for use in dishwashing machines. LADDs overcome the caking problem associated with powdered products when stored in a humid environment.
To be effective, LADDs must be capable of pouring from its container while not leaking or draining once dispensed into the dispensing cup of a home dishwashing machine. This requires a fluid with thixotropic rheology. That is, the LADD must be much less fluid under static conditions than under the dynamic conditions of dispensing the product from the container or when the product is released from the dispensing cup of an automatic dishwasher. In practice, this means that an LADD must exhibit a higher viscosity at low shear and a lower viscosity at high shear.
The invention involves LADDs that contain a detergent enzyme and have a pH value less than 7.0. Such LADDs can lack phosphate builders, chlorine bleaches, and alkali, each of which is undesirable from the perspective of human and environmental safety. For example, detergents containing phosphate builders, chlorine bleaches, and alkali are highly irritating to the skin and especially to the eyes. Thus, any detergent that can avoid these harmful ingredients while maintaining the ability to clean tableware would be desirable.
The invention is based on the discovery that LADDs containing a detergent enzyme and having a pH value less than 7.0 provide superior cleaning performance when compared to an alkaline LADD containing chlorine bleach and phosphate builders. In other words, non-alkaline LADDs lacking chlorine bleach and phosphate builders can be used to clean tableware effectively. Such LADDs can be used at relatively low dosages to achieve a cleaning performance comparable to that obtained using much higher dosages of, for example, alkaline LADDs containing chlorine bleach and phosphate builders.
The invention also is based on the discovery that LADDs containing a detergent enzyme and having a pH value less than 7.0 exhibit significant enzyme stability when compared to similar detergents having a higher pH value. Thus, LADDs containing a detergent enzyme and having a pH value less than 7.0 would have a longer half-life than comparable alkaline LADDs.
It is noted that the term xe2x80x9cby weightxe2x80x9d as used herein with respect to a particular percent of an ingredient refers to that ingredient as is.
In general, the invention features a liquid automatic dishwashing detergent having a pH value less than 7.0 and containing at least one detergent enzyme. The detergent can be free of chlorine sources and/or phosphate builders. The detergent enzyme can include a protease and/or amylase. The protease can remain greater than 90 percent active after incubating the detergent at 30xc2x0 C. for one week. In addition, the protease can remain greater than 80 percent active after incubating the detergent at 30xc2x0 C. for two weeks. The amylase can remain greater than 35 percent active after incubating the detergent at 30xc2x0 C. for one week. In addition, the amylase can remain greater than 30 percent active after incubating the detergent at 30xc2x0 C. for two weeks. Further, 100 grams of the detergent can clean glasses such that the glasses have a grade value less than about 2.50 for spots after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel (an alkaline LADD product containing phosphates and chlorine) being used as a control set to a reference grade value of 1.90. One hundred grams of the detergent can clean flatware such that the flatware has a grade value less than about 2.50 for spots after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 2.10. One hundred grams of the detergent can clean white plates such that the white plates have a grade value less than about 2.50 for spots after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 1.70. One hundred grams of the detergent can clean gold plates such that the gold plates have a grade value less than about 2.50 for spots after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 1.80. One hundred grams of the detergent can clean glasses such that the glasses have a grade value less than about 2.50 for film after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 1.90. One hundred grams of the detergent can clean flatware such that the flatware has a grade value less than about 2.50 for film after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 1.90. One hundred grams of the detergent can clean white plates such that the white plates have a grade value less than about 2.50 for film after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 1.60. One hundred grams of the detergent can clean gold plates such that the gold plates have a grade value less than about 2.50 for film after performing a standard wash test with 200 grams of Lemon Cascade(trademark) Gel being used as a control set to a reference grade value of 1.80. The pH value can be from about 4.5 to about 6.5 (e.g., from about 5.0 to about 6.5; from about 4.5 to about 6.0; and from about 5.0 to about 6.0). The detergent can contain at least one pH adjusting agent such that the detergent has the pH value. The enzyme can be from about 0.01 percent to about 10.0 percent of the detergent by weight (e.g., from about 0.05 percent to about 5.0 percent). The enzyme can contain an enzyme such as Alcalase(trademark) (a serine protease), Esperase(trademark) (a serine protease), Maxacal(trademark) (a serine protease), Maxapem(trademark) (an engineered serine protease), Maxatase(trademark) (a serine protease), Opticlean(trademark) (a protease), Optimase(trademark) (a protease), and Savinase(trademark) (a serine protease). The detergent can be thixotropic. The detergent can contain at least one thixotropic thickener. The thickener can be from about 0.05 percent to about 10.0 percent of said detergent by weight (e.g., from about 0.2 percent to about 5.0 percent or from about 0.5 percent to about 5.0 percent). The thickener can be cross-linked polycarboxylate polymers and/or xanthan gums. The detergent can contain at least one low foaming nonionic surfactant. The surfactant can be from about 0.01 percent to about 20.0 percent of the detergent by weight (e.g., from about 0.05 percent to about 5.0 percent). The surfactant can be a surfactant selected from the following group: (a) first condensation products, where the first condensation products are condensates from a first mixture containing about one mole of a straight or branched chain fatty alcohol or acid and from about four to about forty moles of ethylene oxide, where the alcohol or acid is saturated or unsaturated, and where the chain of the alcohol or acid contains from about ten to about twenty carbon atoms; (b) second condensation products, where the second condensation products are condensates from a second mixture containing about one mole of alkyl phenol and from about four to about fifty moles of ethylene oxide, where the alkyl chain of the alkyl phenol contains from about eight to about eighteen carbon atoms; (c) polyoxypropylene, polyoxyethylene condensates having the formula R1O(CH2CH2O)x(CH(CH3)CH2O)yR2, where R1 is H or an alkyl group having from one to four carbon atoms, where R2 is H or an alkyl group having from one to four carbon atoms, where x is an integer greater than or equal to one, where y is an integer greater than or equal to one, where the total C2H4O content is from about 20 percent to about 90 percent of the total weight of the polyoxypropylene, polyoxyethylene condensates, and where the molecular weight of the polyoxypropylene, polyoxyethylene condensates is from about 2000 Daltons to about 10,000 Daltons; and (d) capped condensates, where the capped condensates contain the polyoxypropylene, polyoxyethylene condensates capped with at least one capping molecule, the capping molecule being a propylene oxide, butylene oxide, short chain alcohols, and/or short chain fatty acids. The detergent can contain at least one calcium ion source. The calcium ion source can be from about 0.01 percent to about 5.0 percent of the detergent by weight. The detergent can contain at least one enzyme stabilizer. The enzyme stabilizer can be from about 0.01 percent to about 30.0 percent of the detergent by weight. The enzyme stabilizer can be selected from the following group: propylene glycol, sorbitol, fructose, sucrose, glucose, short chain carboxylic acids, salt forms of short chain carboxylic acids, polyhydroxyl compounds, boric acid, soluble salt forms of boric acid, boronic acid, and soluble salt forms of boronic acid. The detergent can contain at least one non-phosphate detergent builder. The non-phosphate detergent builder can be from about 0.5 percent to about 30.0 percent of the detergent by weight (e.g., from about 1.0 percent to about 20.0 percent). The non-phosphate detergent builder can be selected from the following group: citric acid, alkali metal forms of citric acid, and ammonium salt forms of citric acid. The detergent can contain at least one organic dispersant. The dispersant can be from about 0.5 percent to about 30.0 percent of the detergent by weight (e.g., from about 1.0 percent to about 20.0 percent). The dispersant can be a soluble salt of a polymer or copolymer of acrylic acid. The dispersant can be a mixture of soluble salts of one or more acrylic acid polymers or copolymers having a molecular weight less than about 5,000 Daltons and one or more acrylic acid polymers or copolymers having a molecular weight of greater than about 500,000 Daltons. The detergent can contain a mixture of at least one non-phosphate detergent builder and at least one organic dispersant. The mixture can be from about 0.5 percent to about 30.0 percent of said detergent by weight. The detergent can contain, by weight: (a) from about 0.05 percent to about 10.0 percent of a thixotropic thickener, (b) from about 0.00 percent to about 20.0 percent of a low foaming nonionic surfactant, (c) from about 0.01 percent to about 10.0 percent of the enzyme, the enzyme being a protease, (d) from about 0.01 percent to about 5.0 percent of a calcium ion source, (e) from about 0.00 percent to about 30.0 percent of an enzyme stabilizer, (1) from about 0.5 percent to about 30.0 percent of a non-phosphate detergent builder, an organic dispersant, or mixture thereof, (g) a sufficient amount of a pH adjusting agent such that the detergent has the pH value. The detergent can contain, by weight: (a) from about 0.5 percent to about 5.0 percent of a thixotropic thickener, (b) from about 0.05 percent to about 5.0 percent of a low foaming nonionic surfactant, (c) from about 0.05 percent to about 5.0 percent of the enzyme, the enzyme being a protease, (d) from about 0.01 percent to about 1.0 percent of a calcium ion source, (e) from about 0.5 percent to about 10.0 percent of an enzyme stabilizer, (f) from about 1.0 percent to about 20.0 percent of a non-phosphate detergent builder, (g) from about 1.0 percent to about 20.0 percent of a soluble salt of a polymer or copolymer of acrylic, and (h) a sufficient amount of a pH adjusting agent such that the detergent has a pH value from about 5.0 to about 6.5. The detergent can contain, by weight, about 55 percent water, about 7 percent citric acid; about 5 percent propylene glycol; about 2 percent Carbopol(trademark) 676 (a carboxyvinyl polymer); about 8 percent NaOH, 50% aq.; about 1 percent sodium borate decahydrate or about 1 percent sodium borate pentahydrate; about 2 percent sodium citrate; about 2 percent sodium formate; about 0.1 percent calcium chloride; about 5 percent sodium xylene sulfonate, 40% aq.; about 2 percent Pluronic(trademark) 25R2 (a polyalkylene oxide block copolymer); about 10 percent Burcosperse(trademark) AP (a polyacrylate dispersant); about 1 percent Savinase(trademark) 16.0 L; and about 0.1 percent Surcide P(trademark) (hexahydro 1-, 3-, 5-tris 2-hydroxy ethyl-s-triazine).
In another aspect, the invention features a method of cleaning tableware in an automatic dishwashing machine. The method includes dispensing an effective amount of a liquid automatic dishwashing detergent into the dispensing cup of the machine. The detergent contains at least one detergent enzyme and has a pH value less than 7.0.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.